Scanning. You can choose to watch everyone’s tweets go by, or log in to watch only the tweets of those you follow. Thanks to Comet technology, Twitterfall has an especially fast search service. You can alter the speed from 0.3 tweets per second to a mind-scrambling 10 tweets per second.

Keyword tracking. You can see the most popular terms of the moment, and just follow tweets containing those keywords (including hashtags). Or you can enter your own search term (as on the Web-based Twitter service Monitter) to track tweets mentioning it. You can combine keywords, too.

Geo-filtering. You can enter a location to narrow down your display to tweets from that location that also mention keywords you choose (again as with Monitter). The words Mumbai and Chengdu come to mind.

Basic usability. Unlike Monitter, you can use Twitterfall to post tweets yourself, reply to tweets and mark tweets as favorites. Just hovering over a tweet pauses the whole thing. You can also follow a user with one click — a feature some popular clients like Tweetdeck lack. You can filter by language and choose to exclude retweets. You can save favorite searches. And you can customize the appearance of the interface, including the font size.